Polyphenylene ether (hereinafter also referred to as “PPE”) is excellent in terms of processability and productivity, and products or components with desired shapes can be efficiently produced from such polyphenylene ether according to molding methods such as a melt injection molding method or a melt extrusion molding method. Accordingly, polyphenylene ether has been widely used as a material for products or components in the field of electric and electronic materials, automobiles, various types of industrial materials, and wrapping materials for food products. With the diversification of intended uses, it has been desired to produce many types of polyphenylene ethers which are excellent in terms of heat resistance and mechanical characteristics and further have different characteristics such as molecular weight and glass transition temperature.
In general, with regard to polyphenylene ether, there is known the phenomenon that its reduced viscosity increases during thermal processing (see Patent Literatures 1 and 2). Accordingly, a molecular design target at the polymerization stage of polyphenylene ether differs from a molecular design target after thermal processing, and thus, operations often become complicated. Therefore, it has been desired to produce polyphenylene ether, the reduced viscosity of which does not change before and after heating, and which maintains a narrow molecular weight distribution in order to maintain physical properties.
It has been generally thought that, when fluidity is required during processing, a wide molecular weight distribution is favorable. On the other hand, a narrow molecular weight distribution is desirable in terms of physical properties. Hence, it has been desired to produce polyphenylene ether, which achieves both good fluidity during processing and good physical properties, namely, has a narrow molecular weight distribution and excellent fluidity during processing. However, under the current circumstances, sufficient studies have not yet been done with regard to this matter.
Patent Literature 2 discloses a PPE composition, which is formed by adding monoamine to polyphenylene ether powder and then subjecting the obtained mixture to press molding at 250° C. for the purpose of improving photostability.
In addition, Patent Literature 3 discloses a PPE composition, which is formed by subjecting polyphenylene ether that has been denatured with benzylamine to press molding in the presence of benzylamine at 280° C. In this publication, a PPE composition, which maintains mechanical strength and suppresses coloration and viscosity increase during heating, can be obtained.
Moreover, Patent Literature 4 discloses polyphenylene ether and polystyrene-based resin compositions, to which polyamine is added as a weld strength promoter for the purpose of improving weld strength.